ON THE MECHANICAL GAMMA-RELAXATION MODES OF POLYCARBONATE

The secondary (gamma) relaxation modes of the polycarbonate of bisphenol A (PC) in the glassy state are discussed. Dynamic mechanical spectra of PC, its mixtures with plasticizers and oligomers, its blends with tetramethyl polycarbonate, as well as spectra of modified polycarbonates and of PC under stress are shown. The evidence suggests that the motions active in glassy PC are intramolecularly cooperative torsional 'local-mode' motions of backbone segments with about 5-7 monomer units. Cooperativity can be reduced or enhanced; it is controlled by the tightness of the matrix. Intermolecularly the motions are not cooperative.